This project is aimed at understanding the structural characteristics of the lumbar spine by measuring the stiffness characteristics of the elements of the intervertebral joint, as well as the stiffness characteristics of the intervertebral bodies and neural arch segments. Analytical modeling for large general motion of one body relative to another body connected by non-linear springs has been completed. The model is being extended now to include the quasi-static and dynamic characteristics of the bony components. The experimental techniques have been developed to properly clamp and load the intervertebral body. Initial studies have looked at the storage problem for the intervertebral joint soft tissues. We have looked at the viscoelastic character of the intervertebral disc, as well as its properties in tension compression and bending about various axis. Future experimental studies will be aimed at defining all of the intervertebral joint components in terms of non-linear spring elements.